In conventional telecommunications networks, especially mobile communication networks, policy control is applied to users based on inputs from a single credit control server. However, in certain situations it may be necessary to make decisions on policy control using inputs from multiple credit control servers.
Conventional policy and charging control (PCC) architecture, defined in 3GPP specification 23.203 defines the Policy and Charging Control functionality, which encompasses two main functions:
Flow-Based Charging, including charging control and online credit control;
Policy control (e.g. gating control, Quality of Service (QoS) control, QoS signaling, etc.).
The policy and charging control (PCC) functionality comprises the functions of the Policy and Charging Enforcement Function (PCEF), the Bearer Binding and Event Reporting Function (BBERF), the Policy and Charging Rules Function (PCRF), the Application Function (AF), the Traffic Detection Function (TDF), the Online Charging System (OCS), the Offline Charging System (OFCS) and the Subscription Profile Repository (SPR) or the User Data Repository (UDR). UDR replaces SPR when the UDC architecture as defined in TS 23.335 is applied to store PCC related subscription data. In such a deployment scenario, an Ud interface between PCRF and UDR can, e.g., be used to access subscription data in the UDR.
The Policy and Charging Rules Function (PCRF) encompasses policy control decision and flow based charging control functionalities. The PCRF provides network control regarding the service data flow detection, gating, QoS and flow based charging (except credit management) towards the Policy and Charging Enforcement Function (PCEF).
The PCEF encompasses service data flow detection, policy enforcement and flow-based charging functionalities. This functional entity is usually located at the Gateway entity (e.g. GGSN (Gateway GPRS Support Node) in the GPRS case, and PDG (Packet Data Gateway) in the WLAN case). It provides service data flow detection, user plane traffic handling, triggering control plane session management (where the IP-CAN (IP Connectivity Access Network) permits), QoS handling, and service data flow measurement as well as online and offline charging interactions.
The Online Charging System (OCS) performs the Service Data Flow Based Credit Control Function. The Online Charging System is specified in 3GPP TS 32.240.
As mentioned above, in certain situations it may be necessary to make decisions on policy control using inputs from multiple credit control servers. The situation can be further complicated if these multiple credit control servers exist in different networks. In such situations, it may not always be possible to grant direct access to policy control resources to these credit control servers due to security, compatibility or legislative reasons.
A possible solution for the case of mobile networks could be to use the usage monitoring functionality already existing on the Rel-9 3GPP Gx interface (the online policy interface used for provisioning service data flow based on charging rules and uses the diameter protocol) between a Policy and Charging Enforcement Function (PCEF), such as the GGSN (Gateway GPRS Support Node in case of a GPRS network), and the Policy and Charging Rules Function (PCRF) in conjunction with an online charging interface (especially the Gy interface) between the (Policy and Charging Enforcement Function part of the) GGSN and a charging server such as an Online Charging System (OCS). In this way the Policy and Charging Rules Function would receive the usage consumption done by the subscriber and could take policy decisions based on that usage. Several drawbacks to this alternative are the following:
It does not allow inputs from multiple charging servers,
It does not allow inputs from servers that are in a separate network than the parent operator's network.
However, this flexibility is important especially in cases of Virtual Network Operators if it is preferred to do the charging completely in the Virtual Network Operator's network space while the parent operator wishes to charge usage separately and protect its own network resources.